1. Field of the Invention
The present invention relates to a disk drive device including a fluid dynamic bearing unit.
2. Description of the Related Art
In recent years, disk drive devices, such as hard disk drives, generally include a fluid dynamic bearing unit that enables a disk to stably rotate at a fast speed. For example, JP 2008-275074 A discloses a motor including a dynamic bearing, and this motor has a lubricant filled between a sleeve forming a part of a stator, and a shaft forming a part of a rotor. Dynamic pressure generated in the lubricant supports the rotor in a non-contact manner, thereby enabling a smooth fast-speed rotation.
Conversely, there is a demand for the disk drive devices to further increase the recording capacity. An example technique to satisfy this demand is to increase the recording density.
In order to increase the recording density, a clearance between a recording/playing head and a disk surface may be reduced. When, however, this clearance is too narrow, it becomes difficult for the recording/playing head to precisely trace the tracks on the disk even a minute particle sticks on the disk surface, resulting in a read/write error. In the worst case, the recording/playing head is damaged, making the disk drive device inoperable.
One of the causes of such particles is a vaporization of the lubricant included in the fluid dynamic bearing unit due to a high-temperature environment originating from a fast-speed rotation of the disk, i.e., a fast-speed rotation of a motor. The vaporized lubricant diffuses in the disk drive device, leaves a condensation on the disk surface, thereby being deposited thereon.
In addition, with respect to the high-temperature environment, downsizing of the disk drive devices increases the temperature thereof in a use atmosphere, and there is a demand to enable the use of the disk drive devices at a further high temperature, e.g., an atmosphere temperature of equal to or higher than 85 degrees.
Still further, there is a demand to ensure a longer lifetime which is equal to or longer than, for example, five years by elongating a time until the lubricant is vaporized and dissipated.
The present invention has been made in view of the foregoing circumstances, and it is an objective of the present invention to provide a disk drive device which prevents a lubricant included in a fluid dynamic bearing unit from being vaporized and diffusing, and which enables a further increase in a recording capacity.
Moreover, it is another objective of the present invention to provide a disk drive device which suppresses a vaporization of the lubricant included in the fluid dynamic bearing unit to ensure a long lifetime.